The Washington state Supreme Court in a unanimous Thursday morning ruling declared the death penalty unconstitutional, claiming it is unevenly applied based on race.

Gov. Jay Inslee issued a moratorium on the death penalty in 2014, saying it would not be used as long as he remained in office. Washington is one of four states with a capital punishment moratorium, along with Oregon, Colorado and Pennsylvania.

The last person executed in Washington was Cal Coburn Brown in 2010. He fatally stabbed 21-year-old Holly Washna of Burien in 1991 after raping and torturing her.

"This has been a 10-year journey to help lift up our community conversation about the importance of eliminating the death penalty," he told SeattlePI Thursday. "It is impossible to apply the death penalty without racial, economic, social and class biases."

He said that while the Supreme Court provided a legal framework to change the death penalty, it is up to lawmakers to enact reforms to the practice or eliminate it.

But, "we're not even going to accept" any measures that would keep the practice in place, he added.

He pointed to public opinion to show that capital punishment is increasingly unpopular; a poll of voters in July showed that 24 percent of Washington voters supported the death penalty.

"The people in this state are ready (to abolish the death penalty) and they believe it's a matter of conscience," Carlyle said.

He believed abolishment would pass the Legislature during the 2019 session.

If the Legislature were to overturn the death penalty, Washington would become the 20th state and join the District of Columbia in outlawing the practice.

The death penalty was issued by a special sentencing process for those convicted of aggravated first-degree murder. Juries determined after a presentation by attorneys whether enough mitigating circumstances should spare the convicted killer capital punishment. The alternative punishment is life in prison without parole.

The methods of killing a person in Washington were lethal injection or, if the inmate so chose, hanging. The last person killed in the gallows was Charles Rodman Campbell in 1994.

Inmates had challenged Washington's lethal injection before. After a botched execution in Ohio using a three-drug combination, Washington in 2010 changed its default substance to a single lethal drug, though it allowed inmates to choose which method by which they would be killed.

Since 1904, Washington has executed 78 men.

Gregory, who is black, was convicted in 2001 of raping, robbing and killing Harshfield in her home. During his sentencing proceeding, the jury sentenced him to death.

The Supreme Court, in reviewing the death sentence the first time, reversed additional and unrelated rape convictions that were considered in the sentencing and reversed the death sentence because the prosecutor committed misconduct during closing arguments and the rape convictions were improperly lumped in with the murder conviction for consideration.

A new jury sentenced Gregory to death a second time based on the murder conviction. Prosecutors then dismissed the rape charges because the accuser made inconsistent claims.

Washington's capital punishment laws have evolved in the past 45 years. The U.S. Supreme Court nullified death penalty laws in 39 states - including Washington - in 1972.

Washington voters then approved a 1975 ballot initiative requiring mandatory death penalty for specific offenses. The U.S. Supreme Court then held that automatic imposition of capital punishment was unconstitutional. The state Legislature then allowed for a jury to determine whether an offender should be sentenced to death on a case-by-case basis.

That statute was then ruled unconstitutional because it allowed the use of the death penalty for those who pleaded not guilty, but not for those who did plead guilty. Lawmakers refined the law again.

The Supreme Court was required to review each death sentence to ensure it was judiciously applied.

Gregory claimed that his sentence "is random and arbitrary, and ... is impermissibly based on his race and the country of conviction."

Gregory commissioned a study, published in 2014, that found black defendants were 4 1/2 times more likely to be sentenced to death than white defendants in a similar situation.

"Given the evidence before this court and our judicial notice of implicit and overt racial bias against black defendants in this state, we are confident that the association between race and the death penalty is not attributed to random chance," Fairhurst wrote.

Individual review of each case did not diminish the biases in the system, she argued.

Gregory also appealed for a new trial, but the Supreme Court upheld his conviction.

King County Prosecutor Dan Satterberg said that eliminating the death penalty as an option would bring justice for victims' families faster. While murder cases are often resolved in three to four years or less, death penalty cases can be appealed and litigated for 20 years, he said.

"With this opinion, Washington's four-decade experiment with the death penalty has come to and end," he said, adding that he supports abolishment. "I think the criminal justice system will be stronger without capital punishment."

Furthermore, only a few counties can even afford to pursue death penalty cases, Satterberg said. King County prosecutors most recently recommended the death penalty for three defendants: Michele Anderson and Joseph McEnroe for the 2007 Christmas Eve Carnation massacre of six family members; and Christopher Monfort, who killed Seattle Police Officer Timothy Brenton on Halloween 2009.

The King County cases on death row are Dayva Cross, who killed his wife and two teenage stepdaughters in Snoqualmie in 1999, and Connor Schierman, who in 2006 killed Olga Milkin, her two young sons and her sister in Kirkland before burning down their house.

But victims' families can still find closure in a "slow death sentence" for killers who spend their lives in prison, Satterberg said.

"This opinion puts us on the right side of history," he said. "The death penalty is an anachronism from another era."

Seattle Mayor Jenny Durkan expressed her support for the decision in a written statement.

"As a former prosecutor and criminal defense lawyer, I saw that the death penalty did not work and perpetuated racial and social injustice," she wrote. "In reality, the death penalty does not deter crime, does real harm in delaying justice for victims and communities and does not reflect our best values - it also diverts resources from valuable and effective public safety initiatives."